CN115142055B - Hydrophobic chemical conversion film forming liquid and aluminum alloy surface treatment method - Google Patents

Abstract

The invention relates to a hydrophobic chemical conversion film forming liquid and an aluminum alloy surface treatment method. The hydrophobic chemical conversion film forming solution comprises trivalent chromium salt, fluorozirconate, an additive and water; the additive is fluotitanic acid and/or fluotitanate. The invention also provides an aluminum alloy surface treatment method, which comprises the following steps: pretreatment: removing impurities from the surface of the aluminum alloy; coating: placing aluminum alloy into the hydrophobic chemical conversion film forming liquid for chemical conversion treatment so as to form a hydrophobic chemical conversion film on the surface of the aluminum alloy; natural aging: and (3) cleaning the coated aluminum alloy, and naturally aging in a normal-temperature environment. The invention solves the problems of high toxicity, poor corrosion resistance and the like of the existing metal surface chemical conversion film.

Description

A hydrophobic chemical conversion film-forming liquid and aluminum alloy surface treatment method

Technical field

The invention relates to the technical field of aluminum alloy surface treatment, and specifically relates to a hydrophobic chemical conversion film-forming liquid and an aluminum alloy surface treatment method.

Background technique

Aluminum alloy is currently the most widely used lightweight metal structural material in the world. In order to meet the requirements of mechanical and other properties, various alloying elements such as Cu, Mg, Zn, and Si are usually added to aluminum alloys. However, due to the addition of a large number of alloying elements, the corrosion resistance of most aluminum alloys decreases and cannot meet the requirements of industrial applications. Therefore, most aluminum alloys require certain surface treatments before they can be put into use.

Common aluminum alloy surface treatment processes include: electroplating, chemical conversion, anodizing, micro-arc oxidation, laser cladding and sol-gel, etc. Among them, chemical conversion coating treatment does not require an external power supply, has simple process operations, low production costs, and has no obvious impact on the mechanical properties of the substrate, and is widely used in industrial production. Among them, chromate conversion coating is the chemical conversion coating with the longest application, best corrosion resistance and self-healing function. It has been widely used for a long time in the past.

However, long-term practical research has found that the hexavalent chromium ions contained in chromate are carcinogenic and have serious harm to humans, animals and the natural environment. The European Union environmental protection organization comprehensively banned the commercial application of hexavalent chromium conversion coatings in 2017, and the United States, Japan and other countries also have stricter restrictions on hexavalent chromium. As a result, green and environmentally friendly chromium-free conversion and chemical conversion processes came into being. Among them, chromium-free conversion coatings mainly include zirconate, phosphate, molybdate, titanate, cobaltate and rare earth salt conversion coatings, etc. However, chromium-free conversion coatings are looser, have poor corrosion resistance, or have cumbersome procedures and poor protection. The effect and application range are not as good as chromate conversion coating.

Contents of the invention

One of the purposes of the present invention is to provide a hydrophobic chemical conversion film-forming liquid to solve the problems of high toxicity and poor corrosion resistance of existing chemical conversion films on metal surfaces; the second purpose is to provide an aluminum alloy surface treatment method, To improve the corrosion resistance of aluminum alloys.

In order to achieve the above objects, the technical solutions adopted by the present invention are as follows:

A hydrophobic chemical conversion membrane fluid including trivalent chromium salt, fluorozirconate, additives and water;

The additive is fluorotitanic acid (H ₂ TiF ₆ ) and/or fluorotitanate.

Preferably, the trivalent chromium salt includes one or more of chromium sulfate (Cr ₂ (SO ₄ ) ₃ ), chromium nitrate (Cr(NO ₃ ) ₃ ) and chromium chloride (CrCl ₃ ).

Preferably, the fluorozirconate includes one or both of potassium fluorozirconate (K ₂ ZrF ₆ ) and sodium fluorozirconate (Na ₂ ZrF ₆ ).

Preferably, the fluorotitanate is potassium fluorotitanate (K ₂ TiF ₆ ).

Preferably, the concentration of the trivalent chromium salt is 0.5~5g/L, the concentration of the fluorozirconate is 1~10g/L, and the concentration of the additive is 0.5~5g/L.

The invention also provides an aluminum alloy surface treatment method, which includes the following steps:

S1. Pretreatment: perform impurity removal treatment on the aluminum alloy surface;

S2. Coating: adjust the pH value of the hydrophobic chemical conversion film-forming liquid of the present invention to acidic, and then put the aluminum alloy into the acidic hydrophobic chemical conversion film-forming liquid for chemical conversion treatment to form hydrophobicity on the surface of the aluminum alloy chemical conversion coating;

S3. Natural aging: Clean the coated aluminum alloy and place it in a normal temperature environment for natural aging.

Among them, the chemical conversion film formed on the surface of the aluminum alloy is colorless.

Preferably, in S2, the temperature of the chemical conversion treatment is 20°C to 60°C. In this temperature range, the film formation rate can be effectively controlled, so that the film layer grows quickly and uniformly, and the treatment time is 60 to 600 seconds.

Preferably, in S1, the pretreatment includes degreasing, alkali washing, pickling and rinsing the aluminum alloy in sequence;

Among them, a degreasing cleaning agent is used for cleaning treatment, the cleaning temperature is 50°C~60°C, and the cleaning time is 30~120 seconds; alkali cleaning (to fully remove the surface rolling deformation layer and part of the second phase particles) uses 5 %~10% (wt.) sodium hydroxide (NaOH) solution for treatment, the alkali washing temperature is 30℃~40℃, the alkali washing time is 10~60 seconds; the pickling uses 30%~40% (vol.) nitric acid (HNO ₃ ) solution, the pickling temperature is 20℃~30℃, the pickling time is 10~60 seconds; deionized water is used for rinsing, the rinsing temperature is 70℃~80℃, the rinsing time is 10~60 seconds .

Preferably, in the S3, the natural aging time is 48 to 120 hours.

Preferably, the thickness of the chemical conversion film formed on the surface of the aluminum alloy is 50 nm to 150 nm, and the water contact angle of the chemical conversion film is greater than 100°.

Beneficial effects of the present invention:

1) The hydrophobic chemical conversion film-forming liquid of the present invention uses chromium salt, fluorozirconate and additives as the main components of the film-forming liquid. The chromium salt has low toxicity, good corrosion resistance, high temperature resistance, certain conductivity and adhesion. Focusing on its advantages, fluorozirconate serves as an oxidant and film-forming agent, mainly used to provide fluoride ions to dissolve the aluminum matrix, thereby promoting the film-forming reaction. The additive acts as a film-forming accelerator and can passivate the delicate structure of the film layer. , the porosity is reduced, and a more stable oxide is introduced into the film layer, so that the nanochemical conversion film made on the metal surface has good hydrophobic properties, effectively improves the corrosion resistance of the metal surface, and is green and environmentally friendly Advantages: It solves the problems of high toxicity and poor corrosion resistance of existing chemical conversion coatings on metal surfaces;

2) The aluminum alloy surface treatment method of the present invention puts the aluminum alloy into a hydrophobic chemical conversion film liquid, causing the chemical conversion film liquid to chemically react with the aluminum alloy surface, thereby forming a chemical conversion film on the aluminum alloy surface. , experimental studies have proven that the chemical conversion film formed on the surface of aluminum alloy has good hydrophobic properties, significantly improves the corrosion resistance of aluminum alloy, and extends the service life of aluminum alloy. The preparation method has the advantages of simple process, mild conditions, It has the advantages of short film formation time, green environmental protection and low production cost. It is suitable for industrial production and has promotion and application value in the field of aluminum alloy surface treatment technology.

Description of drawings

Figure 1 is a scanning electron microscope morphology (10 μm) of the 5056 aluminum foil treated in Example 1;

Figure 2 is a scanning electron microscope morphology (1 μm) of the 5056 aluminum foil treated in Example 1;

Figure 3 is a scanning electron microscope morphology (10 μm) of the 5056 aluminum foil treated in Example 2;

Figure 4 is a scanning electron microscope morphology (1 μm) of the 5056 aluminum foil treated in Example 2;

Figure 5 is a scanning electron microscope morphology (10 μm) of the 5056 aluminum foil treated in Example 3;

Figure 6 is a scanning electron microscope morphology (1 μm) of the 5056 aluminum foil treated in Example 3;

Figure 7 is a scanning electron microscope morphology (10 μm) of the 5056 aluminum foil treated in Example 4;

Figure 8 is a scanning electron microscope morphology (1 μm) of the 5056 aluminum foil treated in Example 4;

Figure 9 is a scanning electron microscope morphology (10 μm) of the 5056 aluminum foil treated in Example 5;

Figure 10 is a scanning electron microscope morphology (2 μm) of the 5056 aluminum foil treated in Example 5;

Figure 11 is a macroscopic morphology diagram of the 5056 aluminum foil treated in Example 1 after being subjected to a 5% neutral salt spray test;

Figure 12 is a diagram showing the results of the water contact angle test on the 5056 aluminum foil treated in Examples 1 to 5;

Figure 13 is the electrochemical impedance spectrum measured in 3.5% (wt%) NaCl aqueous solution of the 5056 aluminum foil treated in Examples 1 to 5;

Figure 14 is an electrochemical polarization curve measured in a 3.5% (wt%) NaCl aqueous solution of the 5056 aluminum foil treated in Examples 1 to 5;

Figure 15 is a graph showing the results of a potassium dichromate drip test on the 5056 aluminum foil treated in Example 1, Example 6 and Example 7.

Detailed ways

The implementation of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention.

Example 1

An aluminum alloy surface treatment method includes the following steps:

S1. Preprocessing:

1) Degreasing treatment: Put the entire 5056 aluminum foil into a 10wt.% degreasing cleaning agent, keep it at a constant temperature of 60°C for 30 seconds to perform degreasing and degreasing treatment, take it out and rinse it in deionized water at 80°C for 30 seconds;

2) Alkali washing treatment: Put the deoiled 5056 aluminum foil into a 10wt.% NaOH aqueous solution, keep it at a constant temperature of 40°C for 30s, take it out and rinse it in deionized water at 80°C for 30s;

3) Pickling treatment: Put the alkali-washed 5056 aluminum foil into a 30 vol.% HNO ₃ aqueous solution for 30 s of deoxidation and ash removal, then take it out and rinse it in 80°C deionized water for 30 s;

4) Rinsing treatment: Rinse the pickled 5056 aluminum foil with deionized water, and finally dry it naturally to obtain pretreated 5056 aluminum foil;

S2. Coating: Use 1wt.% H ₂ SO ₄ solution to adjust the pH value of the hydrophobic chemical conversion film-forming liquid to 3.5, and then place the pretreated 5056 aluminum foil in S1 into the acidic hydrophobic chemical conversion film-forming liquid. Chemical conversion treatment to form a hydrophobic chemical conversion film on the surface of 5056 aluminum foil. The temperature of the chemical conversion treatment is 40°C and the chemical conversion treatment time is 120S;

Among them, the components of the hydrophobic chemical conversion film-forming liquid in Example 1 are Cr ₂ (SO ₄ ) ₃ , K ₂ ZrF ₆ , H ₂ TiF ₆ and water, and the concentration of Cr ₂ (SO ₄ ) ₃ is 2g/L. , the concentration of K ₂ ZrF ₆ is 4g/L, and the concentration of H ₂ TiF ₆ is 2g/L;

S3. Natural aging: After the coating is completed, rinse the 5056 aluminum foil with deionized water, and then place it in a normal temperature environment for natural air drying and aging for 48 hours to obtain a 5056 aluminum foil with a colorless chemical conversion film formed on the surface.

Example 2

An aluminum alloy surface treatment method includes the following steps:

S1. Preprocessing:

1) Degreasing treatment: Put the entire 5056 aluminum foil into 10wt.% degreasing cleaning agent, keep it at a constant temperature of 60°C for 30 seconds to remove oil and degreasing, take it out and rinse it in deionized water at 80°C for 30 seconds. ;

2) Alkali washing treatment: Put the deoiled 5056 aluminum foil into a 10wt.% NaOH aqueous solution, keep it at a constant temperature of 40°C for 30s, take it out and rinse it in deionized water at 80°C for 30s;

3) Pickling treatment: Put the alkali-washed 5056 aluminum foil into a 30 vol.% HNO ₃ aqueous solution for 30 s of deoxidation and ash removal, then take it out and rinse it in 80°C deionized water for 30 s;

4) Rinsing treatment: Rinse the pickled 5056 aluminum foil with deionized water, and finally dry it naturally to obtain pretreated 5056 aluminum foil;

S2. Coating: Use 1wt.% H ₂ SO ₄ solution to adjust the pH value of the hydrophobic chemical conversion film-forming liquid to 2.0. Place the pretreated 5056 aluminum foil in S1 into the acidic hydrophobic chemical conversion film-forming liquid for chemical treatment. Conversion treatment to form a chemical conversion film on the surface of 5056 aluminum foil. The temperature of the chemical conversion treatment is 40°C and the time of the chemical conversion treatment is 120S;

Among them, the components of the hydrophobic chemical conversion film-forming liquid in Example 2 are Cr ₂ (SO ₄ ) ₃ , Na ₂ ZrF ₆ , K ₂ TiF ₆ and water, and the concentration of Cr ₂ (SO ₄ ) ₃ is 2g/L. , the concentration of Na ₂ ZrF ₆ is 4g/L, and the concentration of K ₂ TiF ₆ is 2g/L;

S3. Natural aging: After the coating is completed, rinse the 5056 aluminum foil with deionized water, and then place it in a normal temperature environment for natural air drying and aging for 48 hours to obtain a 5056 aluminum foil with a colorless chemical conversion film formed on the surface.

Example 3

An aluminum alloy surface treatment method includes the following steps:

S1. Preprocessing:

1) Degreasing treatment: Put the entire 5056 aluminum foil into 10wt.% degreasing cleaning agent, keep it at a constant temperature of 60°C for 30 seconds to remove oil and degreasing, take it out and rinse it in deionized water at 80°C for 30 seconds. ;

2) Alkali washing treatment: Put the deoiled 5056 aluminum foil into a 10wt.% NaOH aqueous solution, keep it at a constant temperature of 40°C for 30s, take it out and rinse it in deionized water at 80°C for 30s;

3) Pickling treatment: Put the alkali-washed 5056 aluminum foil into a 30 vol.% HNO ₃ aqueous solution for 30 s of deoxidation and ash removal, then take it out and rinse it in 80°C deionized water for 30 s;

4) Rinsing treatment: Rinse the pickled 5056 aluminum foil with deionized water, and finally dry it naturally to obtain pretreated 5056 aluminum foil;

S2. Coating: Use 1wt.% H ₂ SO ₄ solution to adjust the pH value of the hydrophobic chemical conversion film-forming liquid to 3.0. Place the pretreated 5056 aluminum foil in S1 into the acidic hydrophobic chemical conversion film-forming liquid for chemical treatment. Conversion treatment to form a chemical conversion film on the surface of 5056 aluminum foil. The temperature of the chemical conversion treatment is 40°C and the time of the chemical conversion treatment is 120S;

Among them, the components of the hydrophobic chemical conversion film-forming liquid in Example 3 are Cr ₂ (SO ₄ ) ₃ , Na ₂ ZrF ₆ , H ₂ TiF ₆ and water, and the concentration of Cr ₂ (SO ₄ ) ₃ is 2g/L. , the concentration of Na ₂ ZrF ₆ is 2g/L, and the concentration of H ₂ TiF ₆ is 2g/L;

S3. Natural aging: After the coating is completed, rinse the 5056 aluminum foil with deionized water, and then place it in a normal temperature environment for natural air drying and aging for 48 hours to obtain a 5056 aluminum foil with a colorless chemical conversion film formed on the surface.

Example 4

An aluminum alloy surface treatment method includes the following steps:

S1. Preprocessing:

1) Degreasing treatment: Put the entire 5056 aluminum foil into 10wt.% degreasing cleaning agent, keep it at a constant temperature of 60°C for 30 seconds to remove oil and degreasing, take it out and rinse it in deionized water at 80°C for 30 seconds. ;

2) Alkali washing treatment: Put the deoiled 5056 aluminum foil into a 10wt.% NaOH aqueous solution, keep it at a constant temperature of 40°C for 30s, take it out and rinse it in deionized water at 80°C for 30s;

3) Pickling treatment: Put the alkali-washed 5056 aluminum foil into a 30 vol.% HNO ₃ aqueous solution for 30 s of deoxidation and ash removal, then take it out and rinse it in 80°C deionized water for 30 s;

4) Rinsing treatment: Rinse the pickled 5056 aluminum foil with deionized water, and finally dry it naturally to obtain pretreated 5056 aluminum foil;

S2. Coating: Use 1wt.% H ₂ SO ₄ solution to adjust the pH value of the hydrophobic chemical conversion into film liquid to 4.0. Place the pretreated 5056 aluminum foil in S1 into the acidic hydrophobic chemical conversion into film liquid for chemical treatment. Conversion treatment to form a chemical conversion film on the surface of 5056 aluminum foil. The temperature of the chemical conversion treatment is 40°C and the time of the chemical conversion treatment is 120S;

Among them, the components of the hydrophobic chemical conversion film-forming liquid in Example 4 are K ₂ ZrF ₆ , H ₂ TiF ₆ and water, the concentration of Cr(NO ₃ ) ₃ is 2g/L, and the concentration of K ₂ ZrF ₆ is 2g/L, the concentration of H ₂ TiF ₆ is 2g/L;

S3. Natural aging: After the coating is completed, rinse the 5056 aluminum foil with deionized water, and then place it in a normal temperature environment for natural air drying and aging for 48 hours to obtain a 5056 aluminum foil with a colorless chemical conversion film formed on the surface.

Example 5

An aluminum alloy surface treatment method includes the following steps:

S1. Preprocessing:

1) Degreasing treatment: Put the entire 5056 aluminum foil into 10wt.% degreasing cleaning agent, keep it at a constant temperature of 60°C for 30 seconds to remove oil and degreasing, take it out and rinse it in deionized water at 80°C for 30 seconds. ;

2) Alkali washing treatment: Put the deoiled 5056 aluminum foil into a 10wt.% NaOH aqueous solution, keep it at a constant temperature of 40°C for 30s, take it out and rinse it in deionized water at 80°C for 30s;

3) Pickling treatment: Put the alkali-washed 5056 aluminum foil into a 30 vol.% HNO ₃ aqueous solution for 30 s of deoxidation and ash removal, then take it out and rinse it in 80°C deionized water for 30 s;

4) Rinsing treatment: Rinse the pickled 5056 aluminum foil with deionized water, and finally dry it naturally to obtain pretreated 5056 aluminum foil;

S2. Coating: Use 1wt.% H ₂ SO ₄ solution to adjust the pH value of the hydrophobic chemical conversion film-forming liquid to 5.0. Place the pretreated 5056 aluminum foil in S1 into the acidic hydrophobic chemical conversion film-forming liquid for chemical treatment. Conversion treatment to form a chemical conversion film on the surface of 5056 aluminum foil. The temperature of the chemical conversion treatment is 40°C and the time of the chemical conversion treatment is 120S;

Among them, the components of the hydrophobic chemical conversion film-forming liquid in Example 5 are CrCl ₃ , K ₂ ZrF ₆ , H ₂ TiF ₆ and water. The concentration of CrCl ₃ is 2g/L, and the concentration of K ₂ ZrF ₆ is 2g/L. L, the concentration of H ₂ TiF ₆ is 2g/L;

S3. Natural aging: After the coating is completed, rinse the 5056 aluminum foil with deionized water, and then place it in a normal temperature environment for natural air drying and aging for 48 hours to obtain a 5056 aluminum foil with a colorless chemical conversion film formed on the surface.

Example 6

An aluminum alloy surface treatment method includes the following steps:

S1. Preprocessing:

5) Degreasing treatment: Put the entire 5056 aluminum foil into 10wt.% degreasing cleaning agent, keep it at a constant temperature of 60°C for 30 seconds to remove oil and degreasing, take it out and rinse it in deionized water at 80°C for 30 seconds. ;

6) Alkali washing treatment: Put the deoiled 5056 aluminum foil into a 10wt.% NaOH aqueous solution, keep it at a constant temperature of 40°C for 30s, take it out and rinse it in deionized water at 80°C for 30s;

7) Pickling treatment: Put the alkali-washed 5056 aluminum foil into a 30 vol.% HNO ₃ aqueous solution for 30 s of deoxidation and ash removal, then take it out and rinse it in 80°C deionized water for 30 s;

8) Rinsing treatment: Rinse the pickled 5056 aluminum foil with deionized water, and finally dry it naturally to obtain pretreated 5056 aluminum foil;

S2. Coating: Use 1wt.% H ₂ SO ₄ solution to adjust the pH value of the hydrophobic chemical conversion film-forming liquid to 3.5, and then place the pretreated 5056 aluminum foil in S1 into the acidic hydrophobic chemical conversion film-forming liquid. Chemical conversion treatment to form a hydrophobic chemical conversion film on the surface of 5056 aluminum foil. The temperature of the chemical conversion treatment is 40°C and the chemical conversion treatment time is 120S;

Among them, the components of the hydrophobic chemical conversion film-forming liquid in Example 6 are Cr ₂ (SO ₄ ) ₃ , K ₂ ZrF ₆ , H ₂ TiF ₆ and water, and the concentration of Cr ₂ (SO ₄ ) ₃ is 0.5g/ L, the concentration of K ₂ ZrF ₆ is 1g/L, and the concentration of H ₂ TiF ₆ is 0.5g/L;

S3. Natural aging: After the coating is completed, rinse the 5056 aluminum foil with deionized water, and then place it in a normal temperature environment for natural air drying and aging for 48 hours to obtain a 5056 aluminum foil with a colorless chemical conversion film formed on the surface.

Example 7

An aluminum alloy surface treatment method includes the following steps:

S1. Preprocessing:

9) Degreasing treatment: Put the entire 5056 aluminum foil into 10wt.% degreasing cleaning agent, keep it at a constant temperature of 60°C for 30 seconds to remove oil and degreasing, take it out and rinse it in deionized water at 80°C for 30 seconds. ;

10) Alkali washing treatment: Put the deoiled 5056 aluminum foil into a 10wt.% NaOH aqueous solution, keep it at a constant temperature of 40°C for 30s, take it out and rinse it in deionized water at 80°C for 30s;

11) Pickling treatment: Put the alkali-washed 5056 aluminum foil into a 30 vol.% HNO ₃ aqueous solution for 30 s of deoxidation and ash removal, then take it out and rinse it in 80°C deionized water for 30 s;

12) Rinsing treatment: Rinse the pickled 5056 aluminum foil with deionized water, and finally dry it naturally to obtain pretreated 5056 aluminum foil;

S2. Coating: Use 1wt.% H ₂ SO ₄ solution to adjust the pH value of the hydrophobic chemical conversion film-forming liquid to 3.5, and then place the pretreated 5056 aluminum foil in S1 into the acidic hydrophobic chemical conversion film-forming liquid. Chemical conversion treatment to form a hydrophobic chemical conversion film on the surface of 5056 aluminum foil. The temperature of the chemical conversion treatment is 40°C and the chemical conversion treatment time is 120S;

Among them, the components of the hydrophobic chemical conversion film-forming liquid in Example 7 are Cr ₂ (SO ₄ ) ₃ , K ₂ ZrF ₆ , H ₂ TiF ₆ and water, and the concentration of Cr ₂ (SO ₄ ) ₃ is 5g/L. , the concentration of K ₂ ZrF ₆ is 10g/L, and the concentration of H ₂ TiF ₆ is 5g/L;

S3. Natural aging: After the coating is completed, rinse the 5056 aluminum foil with deionized water, and then place it in a normal temperature environment for natural air drying and aging for 48 hours to obtain a 5056 aluminum foil with a colorless chemical conversion film formed on the surface.

Detection and analysis

1. Morphological observation

A scanning electron microscope was used to observe the morphology of the 5056 aluminum foil treated in Examples 1 to 5, and the results are shown in Figures 1 to 10.

It can be seen from Figure 1 to Figure 10 that the chemical conversion film formed on the surface of 5056 aluminum foil after treatment in Examples 1 to 5 is dense and uniform. Due to the generation of hydrogen during the coating process, the chemical conversion film on the surface of 5056 aluminum foil There are a few pores in the layer, but the overall surface is relatively smooth, and no defects such as cracking are found.

2. Salt spray test

The 5056 aluminum foil without coating treatment and the 5056 aluminum foil treated in Example 1 were subjected to a salt spray test. The results are shown in Figure 11.

From the observation in Figure 11, it can be seen that the surface of the 5056 aluminum foil substrate that has not been coated has obvious corrosion spots and corrosion products after 48 hours, while the surface of the 5056 aluminum foil that has been coated still shows no obvious signs of corrosion after 860 hours. This effectively proves that coating can effectively improve the corrosion resistance of 5056 aluminum foil.

3. Contact angle test

The 5056 aluminum foil treated in Examples 1 to 5 was subjected to multiple water contact angle tests, and the results are shown in Figure 12.

From the analysis in Figure 12, it can be seen that the average water contact angle on the surface of the 5056 aluminum foil treated in Example 1 is about 107°, and the average water contact angle on the surface of the 5056 aluminum foil treated in Example 2 is about 87°. , the average water contact angle of the treated 5056 aluminum foil surface in Example 3 is about 106°, the average water contact angle of the treated 5056 aluminum foil surface in Example 4 is about 103°, and the average water contact angle of the treated 5056 aluminum foil surface in Example 5 is about 103°. The average water contact angle on the surface of the 5056 aluminum foil is about 106°, which shows good hydrophobic properties.

4. Electrochemical impedance and electrochemical polarization testing

The uncoated 5056 aluminum foil and the 5056 aluminum foil treated in Examples 1 to 5 were subjected to electrochemical impedance and electrochemical polarization tests. The results are shown in Figures 13 and 14.

From the analysis in Figure 13, it can be seen that in the NaCl solution, the electrochemical impedance mode value of the 5056 aluminum foil treated in Example 1 reached more than 10 ⁵ Ωcm ^2. Compared with the uncoated 5056 aluminum foil substrate, the impedance mode value Improved by 2-3 orders of magnitude; the electrochemical impedance mode value of the 5056 aluminum foil treated in Examples 2 to 5 has reached more than 10 ⁴ Ωcm ^2. Compared with the uncoated 5056 aluminum foil substrate, the impedance mode value is improved. 1~2 orders of magnitude.

From the analysis in Figure 14, it can be seen that in 3.5% NaCl solution, the self-corrosion current density of the 5056 aluminum foil treated in Example 1 is less than 10 ^-7 Acm ^-2 , which is 1 higher than that of the uncoated 5056 aluminum foil substrate. ~2 orders of magnitude; the self-corrosion current density of the treated 5056 aluminum foil in Example 2 is less than 10 ^-6 Acm ^-2 , which is significantly higher than that of the uncoated 5056 aluminum foil substrate, and its self-corrosion potential is -1.08V, compared with 0.18V higher than that of the uncoated 5056 aluminum foil substrate; the self-corrosion current density of the treated 5056 aluminum foil in Example 3 is less than 10 ^-6 Acm ^-2 , which is significantly higher than that of the uncoated 5056 aluminum foil substrate, and its self-corrosion potential is -0.94V, which is 0.32V higher than that of the uncoated 5056 aluminum foil substrate; the self-corrosion current density of the treated 5056 aluminum foil in Example 4 is less than 10 ^-6 Acm ^-2 , which is significantly higher than that of the uncoated 5056 aluminum foil. substrate, and its self-corrosion potential is -1.07V, which is 0.19V higher than that of the uncoated 5056 aluminum foil substrate; the self-corrosion current density of the treated 5056 aluminum foil in Example 5 is less than 10 ^-6 Acm ^-2 , which is significantly higher For the uncoated 5056 aluminum foil substrate, its self-corrosion potential is -1.09V, which is 0.17V higher than that of the uncoated 5056 aluminum foil substrate.

5. Potassium dichromate drop test

The uncoated 5056 aluminum foil and the 5056 aluminum foil treated in Example 1, Example 6 and Example 7 were subjected to a potassium dichromate drop test at 25°C. The results are shown in Figure 15.

From the analysis in Figure 15, it can be seen that the 5056 aluminum foil treated in Example 1 can withstand the 300s potassium dichromate titration test, and the 5056 aluminum foil treated in Examples 6 and 7 can withstand the 120s potassium dichromate titration test, while The potassium dichromate drop test of the uncoated 5056 aluminum foil substrate is about 30 seconds, which proves that the corrosion resistance of the aluminum foil is greatly improved after coating.

The aluminum alloy surface treatment method of the present invention places the aluminum alloy in the hydrophobic chemical conversion film-forming liquid of the present invention at a lower temperature of 20~60°C, a shorter time of 60~600 s, and under atmospheric environmental conditions. It can be converted into a layer of chemical conversion film with a water contact angle greater than 100 and a thickness of 50~150nm on the surface of the aluminum alloy. Experimental studies have proven that aluminum alloys with a chemical conversion film formed on the surface can withstand 860 hours of neutral salt spray testing, and the electrochemical impedance modulus value and self-corrosion current are significantly higher than those of the substrate, thus effectively improving the performance of aluminum alloys. It has corrosion resistance, and the treatment method has the advantages of being simple, easy, green and environmentally friendly. It has promotion and application value in the field of aluminum alloy surface treatment technology.

The above embodiments are only preferred embodiments to fully illustrate the present invention, and the protection scope of the present invention is not limited thereto. Equivalent substitutions or transformations made by those skilled in the art on the basis of the present invention are within the protection scope of the present invention.

Claims (6)

1. An aluminum alloy surface treatment method, characterized in that it includes the following steps: S1. Pretreatment: perform impurity removal treatment on the aluminum alloy surface; S2. Coating: Adjust the pH value of the hydrophobic chemical conversion film-forming liquid to acidic, and then put the aluminum alloy into the acidic hydrophobic chemical conversion film-forming liquid for chemical conversion treatment to form a hydrophobic chemical conversion film on the surface of the aluminum alloy; The hydrophobic chemical conversion film-forming liquid includes trivalent chromium salt, fluorozirconate, additives and water; the additive is fluotitanic acid; S3. Natural aging: Clean the coated aluminum alloy and place it in a normal temperature environment for natural aging. In the S1, the pretreatment includes degreasing, alkali washing, pickling and rinsing the aluminum alloy in sequence; Among them, a degreasing cleaning agent is used for cleaning treatment, the cleaning temperature is 50°C~60°C, and the cleaning time is 30~120 seconds; alkali cleaning uses 5%~10% (wt.) sodium hydroxide solution, and the alkali cleaning process is The washing temperature is 30℃~40℃, the alkali washing time is 10~60 seconds; the pickling uses 30%~40% (vol.) nitric acid solution, the pickling temperature is 20℃~30℃, the pickling time is 10 ~60 seconds; deionized water is used for rinsing, the rinsing temperature is 70℃~80℃, and the rinsing time is 10~60 seconds; The thickness of the chemical conversion film formed on the surface of the aluminum alloy is 50nm~150nm, and the water contact angle of the chemical conversion film is greater than 100°. 2. The aluminum alloy surface treatment method according to claim 1, wherein the trivalent chromium salt includes one or more of chromium sulfate, chromium nitrate and chromium chloride. 3. The aluminum alloy surface treatment method according to claim 1, wherein the fluorozirconate includes one or both of potassium fluorozirconate and sodium fluorozirconate. 4. The aluminum alloy surface treatment method according to claim 1, characterized in that the concentration of the trivalent chromium salt is 0.5~5g/L, and the concentration of the fluorozirconate is 1~10g/L, so The concentration of the above additives is 0.5~5g/L. 5. The aluminum alloy surface treatment method according to claim 1, characterized in that in the S2, the temperature of the chemical conversion treatment is 20°C~60°C, and the treatment time is 60~600 seconds. 6. The aluminum alloy surface treatment method according to claim 1, characterized in that, in the S3, the natural aging time is 48 to 120 hours.